KR102338507B1 - Method and apparatus for transmitting and receving downlink control information in wirelss communication system - Google Patents

Abstract

The present disclosure relates to a communication technique that converges a 5G communication system for supporting a higher data rate after a 4G system with IoT technology, and a system thereof. The present disclosure provides intelligent services (eg, smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail business, security and safety-related services, etc.) based on 5G communication technology and IoT-related technology. ) can be applied to The present invention discloses a method and apparatus for reducing power consumption of a terminal and increasing resource use efficiency of a base station at the same time by proposing resource sharing between a data channel and a control channel.

Description

Method and apparatus for transmitting and receiving downlink control information in a wireless communication system

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting and receiving downlink control information.

Efforts are being made to develop an improved 5G communication system or pre-5G communication system in order to meet the increasing demand for wireless data traffic after commercialization of the 4G communication system. For this reason, the 5G communication system or the pre-5G communication system is called a 4G network after (Beyond 4G Network) communication system or an LTE system after (Post LTE) system.

In order to achieve a high data rate, the 5G communication system is being considered for implementation in a very high frequency (mmWave) band (eg, such as a 60 gigabyte (60 GHz) band). In order to alleviate the path loss of radio waves and increase the propagation distance of radio waves in the ultra-high frequency band, in the 5G communication system, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) are used. ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed.

In addition, for network improvement of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud radio access network: cloud RAN), an ultra-dense network (ultra-dense network) , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation Technology development is underway.

In addition, in the 5G system, FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding), which are advanced coding modulation (Advanced Coding Modulation: ACM) methods, and FBMC (Filter Bank Multi Carrier), NOMA, which are advanced access technologies, (non orthogonal multiple access), and sparse code multiple access (SCMA) are being developed.

On the other hand, the Internet is evolving from a human-centered connection network where humans create and consume information to an Internet of Things (IoT) network that exchanges and processes information between distributed components such as objects. Internet of Everything (IoE) technology, which combines big data processing technology through connection with cloud servers, etc. with IoT technology, is also emerging. In order to implement IoT, technology elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. , M2M), and MTC (Machine Type Communication) are being studied. In the IoT environment, an intelligent IT (Internet Technology) service that collects and analyzes data generated from connected objects and creates new values in human life can be provided. IoT is a field of smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart home appliance, advanced medical service, etc. can be applied to

Accordingly, various attempts are being made to apply the 5G communication system to the IoT network. For example, in technologies such as sensor network, machine to machine (M2M), and MTC (Machine Type Communication), 5G communication technology is implemented by techniques such as beam forming, MIMO, and array antenna. there will be The application of cloud radio access network (cloud RAN) as the big data processing technology described above can be said to be an example of convergence of 5G technology and IoT technology.

On the other hand, various methods for improving resource efficiency in the next-generation communication system are continuously being discussed, and in particular, the demand for flexibly using the resource area in which the control channel is transmitted is increasing day by day.

In order to support transmission of downlink and uplink transmission channels in a wireless communication system, downlink control signaling related thereto is required. Control signaling in the conventional 4G Long Term Evolution (LTE) system is a downlink scheduling assignment that includes information necessary for a UE to properly receive, demodulate, and decode a Physical Downlink Shared Channel (PDSCH) and a Physical Uplink Shared Channel (PUSCH) by the UE. Channel) and includes information such as an acknowledgment for an uplink scheduling grant and a Hybrid Automatic Repeat Request (HARQ) for PUSCH that informs about a resource and a transmission format. In LTE, a Physical Downlink Control Channel (PDCCH) exists as a physical layer transmission channel for transmitting downlink scheduling assignment and uplink scheduling grant among them, and it is transmitted over the entire band in the front part of each subframe. That is, the subframe can be divided into a control region and a data region, and the size of the control region is designed to occupy 1, 2, or 3 OFDM (Orthogonal Frequency Division Multiplexing) symbols. The size of the control region expressed by the number of OFDM symbols can be dynamically changed according to special circumstances, such as the size of the system bandwidth and whether a Multimedia Broadcast Multicast Services (MBSFN) subframe for broadcasting is set, which is a Control Format (CFI) Indicator) may be indicated to each terminal.

On the other hand, the 5G wireless communication system intends to support not only the service requiring a high transmission rate, but also a service having a very short transmission delay and a service requiring a high connection density. These scenarios must be able to provide various services with different transmission/reception techniques and transmission/reception parameters in one system to satisfy various user requirements and services, and are added in consideration of forward compatibility. It is important to design the service so that it does not encounter constraints that are limited by the current system. For example, scalable numerology may be used for the interval between subcarriers and it may be supported simultaneously, or various services having different Transmission Time Intervals (TTIs) may be serviced simultaneously in one system. Inevitably, 5G should be able to use time and frequency resources more flexibly, unlike existing LTE.

The PDCCH used in the conventional LTE is not suitable for securing its flexibility in that it is transmitted over the entire band and the size of the control region is cell-specific. Accordingly, in the 5G wireless communication system, a structure in which control channels can be flexibly allocated according to various service requirements is being considered. For example, a control region (CORESET: Control Resource Set) defined by a time and frequency domain in which the 5G downlink control channel is transmitted is not transmitted in the entire band on the frequency axis, but is set in a specific subband and transmitted. On the time axis, the number of OFDM symbols of different sizes may be set and transmitted. A plurality of control regions may exist in one system, and a plurality of control regions may be configured for one terminal. Accordingly, the control region can be efficiently managed according to whether the downlink control signal is transmitted, and thus various services can be flexibly supported.

A method of a terminal according to an embodiment of the present invention for solving the above problems includes the steps of detecting first downlink control information (DCI) indicating downlink scheduling from the entire search space of the terminal, and related to the first DCI determining whether data is mapped on a resource region for transmission of control information, and detecting a second DCI from a search space of the terminal based on whether data is mapped on a resource region for transmission of control information include

In order to solve the above problems, the terminal according to an embodiment of the present invention detects first downlink control information (DCI) indicating downlink scheduling from a transceiver for transmitting and receiving a signal and an entire search space of the terminal, 1 It is determined whether data related to DCI is mapped on a resource region for transmission of control information, and configured to detect a second DCI from a search space of the terminal based on whether data is mapped on a resource region for transmission of control information includes a control unit.

The method of the base station according to an embodiment of the present invention for solving the above problems includes the steps of determining whether a first resource region mapped to data to be transmitted to a terminal overlaps a second resource region for transmitting control information, data Based on the overlapping ratio of the first resource region mapped to the second resource region for transmission of control information, determining whether to map and transmit data on the second resource region, and the terminal through the resource region mapped to the data sending data to

In a base station according to an embodiment of the present invention for solving the above problems, a transceiver for transmitting and receiving a signal, and a first resource region mapped to data to be transmitted to a terminal overlap a second resource region for transmission of control information determines whether the data is mapped on the second resource region and transmitted based on the overlap ratio of the first resource region mapped to data and the second resource region for transmission of control information, and the resource mapped to data and a control unit configured to transmit data to the terminal through the area.

The present invention provides a method for transmitting a data channel and downlink control information for efficiently reusing a control region in a wireless communication system. In addition, by providing a low-power monitoring technique for the downlink control channel, it is possible to significantly reduce the number of blind decodings for the downlink control channel, thereby reducing power consumption of the terminal and enabling an energy-efficient terminal implementation.

1 is a diagram illustrating a basic structure of a time-frequency domain in LTE.
2 is a diagram illustrating PDCCH and EPDCCH, which are downlink control channels of LTE.
3 is a diagram illustrating transmission resources of a 5G downlink control channel.
4 is a diagram illustrating resource region allocation of a 5G downlink control channel.
5 is a diagram illustrating an example of transmitting a PDSCH while reusing a control region considered in 5G.
6 is a view showing a first embodiment of the present invention.
7 is a flowchart illustrating an operation of a terminal according to the first embodiment of the present invention.
8 is a diagram illustrating a second embodiment of the present invention.
9 is a flowchart illustrating an operation of a base station according to a second embodiment of the present invention.
10 is a diagram illustrating a third embodiment of the present invention.
11 is a flowchart illustrating an operation of a base station according to a third embodiment of the present invention.
12 is a block diagram illustrating an internal structure of a terminal according to an embodiment of the present invention.
13 is a block diagram illustrating an internal structure of a base station according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. And the terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the content throughout this specification.

Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, in describing embodiments of the present invention, descriptions of technical contents that are well known in the technical field to which the present invention pertains and are not directly related to the present invention will be omitted. This is to more clearly convey the gist of the present invention without obscuring the gist of the present invention by omitting unnecessary description.

For the same reason, some components are exaggerated, omitted, or schematically illustrated in the accompanying drawings. In addition, the size of each component does not fully reflect the actual size. In each figure, the same or corresponding elements are assigned the same reference numerals.

At this time, it will be understood that each block of the flowchart diagrams and combinations of the flowchart diagrams may be performed by computer program instructions. These computer program instructions may be embodied in a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment, such that the instructions performed by the processor of the computer or other programmable data processing equipment are not described in the flowchart block(s). It creates a means to perform functions. These computer program instructions may also be stored in a computer-usable or computer-readable memory which may direct a computer or other programmable data processing equipment to implement a function in a particular manner, and thus the computer-usable or computer-readable memory. It is also possible that the instructions stored in the flow chart block(s) produce an article of manufacture containing instruction means for performing the function described in the flowchart block(s). The computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to create a computer or other programmable data processing equipment. It is also possible that instructions for performing the processing equipment provide steps for performing the functions described in the flowchart block(s).

Additionally, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing specified logical function(s). It should also be noted that in some alternative implementations it is also possible for the functions recited in blocks to occur out of order. For example, two blocks shown one after another may be performed substantially simultaneously, or the blocks may sometimes be performed in the reverse order according to a corresponding function.

At this time, the term '~ unit' used in this embodiment means software or hardware components such as FPGA or ASIC, and '~ unit' performs certain roles. However, '-part' is not limited to software or hardware. '~' may be configured to reside on an addressable storage medium or may be configured to refresh one or more processors. Accordingly, as an example, '~' indicates components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, components and '~ units' may be implemented to play one or more CPUs in a device or secure multimedia card. Also, in an embodiment, '~ unit' may include one or more processors.

A wireless communication system, for example, 3GPP's HSPA (High Speed Packet Access), LTE (Long Term Evolution or E-UTRA (Evolved Universal Terrestrial Radio Access)), LTE-Advanced (LTE-A), LTE-Pro, 3GPP2 HRPD (High Rate Packet Data), UMB (Ultra Mobile Broadband), and IEEE 802.16e, such as communication standards such as broadband wireless broadband wireless providing high-speed, high-quality packet data service It is evolving into a communication system.

As a representative example of the broadband wireless communication system, in the LTE system, an Orthogonal Frequency Division Multiplexing (OFDM) scheme is employed in a Downlink (DL), and Single Carrier Frequency Division Multiple (SC-FDMA) is used in an Uplink (UL). Access) method is adopted. Uplink refers to a radio link in which a UE (User Equipment) or MS (Mobile Station) transmits data or control signals to a base station (eNode B, or base station (BS)). It means a wireless link that transmits data or control signals. In the multiple access method as described above, the data or control information of each user is divided by allocating and operating the time-frequency resources to which data or control information is to be transmitted for each user so that they do not overlap each other, that is, orthogonality is established. do.

As a future communication system after LTE, that is, the 5G communication system must be able to freely reflect various requirements of users and service providers, so services that simultaneously satisfy various requirements must be supported. Services considered for the 5G communication system include enhanced Mobile Broadband (eMBB), massive machine type communication (mMTC), Ultra Reliability Low Latency Communication (URLLC), etc. There is this.

eMBB aims to provide more improved data transfer rates than the data transfer rates supported by existing LTE, LTE-A or LTE-Pro. For example, in the 5G communication system, the eMBB must be able to provide a maximum data rate of 20 Gbps in the downlink and a maximum data rate of 10 Gbps in the uplink from the viewpoint of one base station. In addition, the 5G communication system must provide the maximum transmission speed and, at the same time, provide the increased user perceived data rate of the terminal. In order to satisfy such a requirement, it is required to improve various transmission and reception technologies, including a more advanced multi-input multi-output (MIMO) transmission technology. In addition, while transmitting signals using a maximum of 20 MHz transmission bandwidth in the 2 GHz band currently used by LTE, the 5G communication system uses a wider frequency bandwidth than 20 MHz in the frequency band of 3 to 6 GHz or 6 GHz or more. Data transfer speed can be satisfied.

At the same time, mMTC is being considered to support application services such as the Internet of Things (IoT) in the 5G communication system. In order to efficiently provide the Internet of Things, mMTC requires large-scale terminal access support within a cell, improved terminal coverage, improved battery life, and reduced terminal cost. Since the Internet of Things is attached to various sensors and various devices to provide communication functions, it must be able to support a large number of terminals (eg, 1,000,000 terminals/km2) within a cell. In addition, since terminals supporting mMTC are highly likely to be located in shaded areas not covered by cells, such as basements of buildings, due to the characteristics of the service, wider coverage is required compared to other services provided by the 5G communication system. A terminal supporting mMTC must be composed of a low-cost terminal, and since it is difficult to frequently exchange the battery of the terminal, a very long battery life time such as 10 to 15 years is required.

Finally, in the case of URLLC, it is a cellular-based wireless communication service used for a specific purpose (mission-critical). For example, remote control of a robot or machine, industrial automation, Unmaned Aerial Vehicle, remote health care, emergency situation A service used for an emergency alert, etc. may be considered. Therefore, the communication provided by URLLC must provide very low latency and very high reliability. For example, a service supporting URLLC must satisfy an air interface latency of less than 0.5 milliseconds, and at the same time has a requirement of a packet error rate of 10-5 or less. Therefore, for a service that supports URLLC, the 5G system must provide a smaller Transmit Time Interval (TTI) than other services, and at the same time, it is designed to allocate wide resources in the frequency band to secure the reliability of the communication link. matters are required

The three services of 5G, namely eMBB, URLLC, and mMTC, can be multiplexed and transmitted in one system. In this case, different transmission/reception techniques and transmission/reception parameters may be used between services to satisfy different requirements of each service.

Hereinafter, frame structures of LTE and LTE-A systems will be described in more detail with reference to the drawings.

1 is a diagram illustrating a basic structure of a time-frequency domain, which is a radio resource domain in which the data or control channel is transmitted in downlink in a system in LTE.

1 , the horizontal axis represents the time domain, and the vertical axis represents the frequency domain. The minimum transmission unit in the time domain is an OFDM symbol. N _symb (101) OFDM symbols are gathered to form one slot 102, and two slots are gathered to form one subframe 103. The length of the slot is 0.5 ms, and the length of the subframe is 1.0 ms. And the radio frame 104 is a time domain unit consisting of 10 subframes. The minimum transmission unit in the frequency domain is a subcarrier, and the bandwidth of the entire system transmission bandwidth consists of a total of N _BW 105 subcarriers. A basic unit of a resource in the time-frequency domain is a resource element (106, Resource Element, RE), which may be represented by an OFDM symbol index and a subcarrier index. A resource block 107 (Resource Block, RB, or Physical Resource Block, PRB) is defined as N _symb (101) consecutive OFDM symbols in the time domain and N _RB (108) consecutive subcarriers in the frequency domain. Accordingly, one RB 108 consists of N _symb x N _RB REs 106 . In general, the minimum transmission unit of data is the RB unit. In the LTE system, in general, N _symb = 7, N _RB = 12, and N _BW and N _RB are proportional to the bandwidth of the system transmission band.

Next, downlink control information (DCI) in LTE and LTE-A systems will be described in detail.

In the LTE system, scheduling information for downlink data or uplink data is transmitted from a base station to a terminal through DCI. DCI is defined in various formats, whether it is scheduling information for uplink data or scheduling information for downlink data, whether it is a compact DCI with a small size of control information, and spatial multiplexing using multiple antennas is applied. It operates by applying a DCI format determined according to whether or not it is DCI for power control. For example, DCI format 1, which is scheduling control information for downlink data, is configured to include at least the following control information.

- Resource allocation type 0/1 flag (Resource allocation type 0/1 flag): Notifies whether the resource allocation method is type 0 or type 1. Type 0 allocates resources in a RBG (resource block group) unit by applying a bitmap method. A basic unit of scheduling in the LTE system is a resource block (RB) expressed by time and frequency domain resources, and the RBG is composed of a plurality of RBs to become a basic unit of scheduling in the type 0 scheme. Type 1 allows to allocate a specific RB within an RBG.

- Resource block assignment: Notifies the RB allocated for data transmission. The resource to be expressed is determined according to the system bandwidth and resource allocation method.

- Modulation and coding scheme (MCS): Notifies the modulation scheme used for data transmission and the size of the transport block, which is data to be transmitted.

- HARQ process number (HARQ process number): Notifies the process number of HARQ.

- New data indicator (New data indicator): Notifies whether HARQ initial transmission or retransmission.

- Redundancy version: Notifies the redundancy version of HARQ.

- Transmit Power Control (TPC) command for PUCCH (Physical Uplink Control CHannel): Notifies a transmit power control command for PUCCH, which is an uplink control channel.

As described above, the DCI transmitted through the downlink control channel includes the following information.

- Downlink scheduling assignment (assignment): PDSCH resource designation, transmission format, HARQ information, spatial multiplexing related control information

-Uplink scheduling grant (grant): PUSCH resource designation, transmission format, HARQ information, PUSCH power control

- Power control command for terminal set

Different control information generally have different DCI message sizes and are classified into different DCI formats. To briefly introduce the DCI format, downlink scheduling assignment information is transmitted in DCI format 1/1A/2/1C/1D/2/2A/2B/2C, and uplink scheduling approval is transmitted in DCI format 0/4. and the power control command is transmitted in DCI format 3/3A. In general, since a plurality of terminals are simultaneously scheduled for downlink and uplink, a plurality of DCI transmissions occur simultaneously.

The DCI is transmitted through a downlink physical control channel, PDCCH or EPDCCH (Enhanced PDCCH), through a channel coding and modulation process.

A CRC (Cyclic Redundancy Check) is attached to the DCI message payload, and the CRC is scrambled with a Radio Network Temporary Identifier (RNTI) corresponding to the identity of the UE. Different RNTIs are used according to the purpose of the DCI message, for example, UE-specific data transmission, a power control command, or a random access response. That is, the RNTI is not explicitly transmitted, but included in the CRC calculation process and transmitted. Upon receiving the DCI message transmitted on the PDCCH, the UE checks the CRC using the assigned RNTI.

Next, a downlink control channel in LTE and LTE-A systems will be described in detail with reference to the drawings.

2 is a diagram illustrating a PDCCH 201 and an Enhanced PDCCH 202 (EPDCCH) that are downlink physical channels through which DCI of LTE is transmitted.

According to FIG. 2, the PDCCH 201 is time-multiplexed with the PDSCH 203, which is a data transmission channel, and is transmitted over the entire system bandwidth. The area of the PDCCH 201 is expressed by the number of OFDM symbols, and the number of OFDM symbols is indicated to the UE by a Control Format Indicator (CFI) transmitted through a Physical Control Format Indicator Channel (PCFICH). By allocating the PDCCH 201 to the OFDM symbol at the beginning of the subframe, the UE can decode the downlink scheduling assignment as soon as possible, and through this, the decoding delay for the DL-SCH (Downlink Shared Channel), that is, the overall downlink There is an advantage in that link transmission delay can be reduced. One PDCCH carries one DCI message, and since a plurality of terminals can be simultaneously scheduled for downlink and uplink, a plurality of PDCCHs are transmitted simultaneously in each cell.

The CRS 204 is used as a reference signal for decoding the PDCCH 201 . The CRS 204 is transmitted in every subframe over the entire band, and scrambling and resource mapping are changed according to a cell ID (Identity). Since the CRS 204 is a reference signal commonly used by all terminals, terminal-specific beamforming cannot be used. Therefore, the multi-antenna transmission method for PDCCH of LTE is limited to open-loop transmission diversity. The number of ports of CRS is implicitly known to the UE from decoding of PBCH (Physical Broadcast Channel).

Resource allocation of the PDCCH 201 is based on a Control-Channel Element (CCE), and one CCE consists of 9 Resource Element Groups (REGs), that is, a total of 36 Resource Elements (REs). The number of CCEs required for a specific PDCCH 201 may be 1, 2, 4, or 8, which depends on the channel coding rate of the DCI message payload. As described above, the number of different CCEs is used to implement link adaptation of the PDCCH 201 .

The UE needs to detect a signal without knowing information about the PDCCH 201. In LTE, a search space indicating a set of CCEs is defined for blind decoding. The search space consists of a plurality of sets at the aggregation level (AL) of each CCE, which is not explicitly signaled but is implicitly defined through a function and subframe number by the UE identity. In each subframe, the UE performs decoding on the PDCCH 201 for all possible resource candidates that can be made from CCEs in the configured search space, and information declared valid for the UE through CRC verification. to process

The search space is classified into a UE-specific search space and a common search space. A group of terminals or all terminals may search the common search space of the PDCCH 201 to receive cell-common control information such as a dynamic scheduling for system information or a paging message. For example, scheduling allocation information of a DL-SCH for transmission of a System Information Block (SIB)-1 including operator information of a cell may be received by examining the common search space of the PDCCH 201 .

According to FIG. 2 , the EPDCCH 202 is frequency-multiplexed with the PDSCH 203 and transmitted. The base station can appropriately allocate the resources of the EPDCCH 202 and the PDSCH 203 through scheduling, thereby effectively supporting coexistence with data transmission for an existing LTE terminal. However, since the EPDCCH 202 is allocated to all one subframe on the time axis and transmitted, there is a problem in terms of transmission delay time. A plurality of EPDCCHs 202 constitute one EPDCCH 202 set, and allocation of the EPDCCH 202 set is made in units of Physical Resource Block (PRB) pairs. The location information for the EPDCCH set is terminal-specifically set, and this is signaled through Remote Radio Control (RRC). A maximum of two sets of EPDCCH 202 may be configured for each UE, and one set of EPDCCH 202 may be configured by being multiplexed to different UEs at the same time.

Resource allocation of the EPDCCH 202 is based on ECCE (Enhanced CCE), and one ECCE may consist of 4 or 8 EREGs (Enhanced REGs), and the number of EREGs per ECCE is CP length and subframe configuration information. depends on One EREG consists of 9 REs, and therefore 16 EREGs may exist per PRB pair. The EPDCCH transmission method is divided into localized/distributed transmission according to the RE mapping method of EREG. The aggregation level of ECCE may be 1, 2, 4, 8, 16, or 32, which is determined by the CP length, subframe configuration, EPDCCH format, and transmission method.

The EPDCCH 202 only supports a UE-specific search space. Therefore, a terminal desiring to receive a system message must search the common search space on the existing PDCCH 201 .

Unlike the PDCCH 201 , in the EPDCCH 202 , a Demodulation Reference Signal (DMRS) 205 is used as a reference signal for decoding. Accordingly, precoding for the EPDCCH 202 may be configured by the base station, and terminal-specific beamforming may be used. Through the DMRS 205, UEs can perform decoding on the EPDCCH 202 without knowing which precoding is used. The EPDCCH 202 uses the same pattern as the DMRS of the PDSCH 203 . However, unlike the PDSCH 203 , the DMRS 205 in the EPDCCH 202 may support transmission using up to four antenna ports. The DMRS 205 is transmitted only in the corresponding PRB through which the EPDCCH is transmitted.

Port configuration information of the DMRS 205 varies depending on the EPDCCH 202 transmission method. In the case of the localized transmission method, the antenna port corresponding to the ECCE to which the EPDCCH 202 is mapped is selected based on the ID of the UE. When different terminals share the same ECCE, that is, when multiuser MIMO (Multiuser MIMO) transmission is used, a DMRS antenna port may be allocated to each terminal. Alternatively, the DMRS 205 may be shared and transmitted. In this case, it may be divided into a DMRS 205 scrambling sequence configured as higher layer signaling. In the case of the distributed transmission method, up to two antenna ports of the DMRS 205 are supported, and the diversity method of the precoder cycling method is supported. The DMRS 205 may be shared for all REs transmitted within one PRB pair.

Next, a search space for downlink control channel transmission in LTE and LTE-A will be described in more detail.

In LTE, the entire PDCCH region is composed of a set of CCEs in the logical region, and a search space composed of a set of CCEs exists. The search space is divided into a common search space and a UE-specific search space, and the search space for LTE PDCCH is defined as shown in Table 1 below as described in 3GPP TS 36.213.

[Table 1]

According to the definition of the search space for the PDCCH described in Table 1 above, the UE-specific search space is not explicitly signaled, but is implicitly defined through a function and subframe number according to the UE identity. In other words, since the UE-specific search space can change according to the subframe number, this means that it can change with time, and through this, a problem that a specific UE cannot use the search space by other UEs among UEs ( It is defined as a blocking problem). If any UE cannot be scheduled in the subframe because all CCEs it examines are already being used by other UEs scheduled in the same subframe, since this search space changes with time, in the next subframe Problems like this may not occur. For example, even if a part of the UE-specific search space of UE#1 and UE#2 overlaps in a specific subframe, since the UE-specific search space changes for each subframe, the overlap in the next subframe is expected to be different can do.

According to the definition of the search space for the PDCCH described above, the common search space is defined as a set of promised CCEs because a certain group of terminals or all terminals must receive the PDCCH. In other words, the common search space does not change according to the identity of the terminal or the subframe number. Although the common search space exists to transmit various system messages, it can also be used to transmit control information of individual terminals. Through this, the common search space can be used as a solution to the problem that the terminal cannot be scheduled due to insufficient resources available in the terminal-specific search space.

The search space is a set of candidate control channels composed of CCEs that the UE should attempt to decode on a given aggregation level, and since there are several aggregation levels that make one bundle with 1, 2, 4, 8 CCEs, the UE has a plurality of have a search space. In the LTE PDCCH, the number of PDCCH candidates to be monitored by the UE in the search space defined according to the aggregation level is defined in Table 2 below.

[Table 2]

According to [Table 2], in the case of the UE-specific search space, the aggregation level {1, 2, 4, 8} is supported, and in this case, {6, 6, 2, 2} PDCCH candidates are each. In the case of the common search space, an aggregation level {4, 8} is supported, and in this case, {4, 2} PDCCH candidates are each. The reason why the common search space supports only the aggregation level of {4, 8} is to improve the coverage characteristics because the system message generally has to reach the cell edge.

DCI transmitted to the common search space is defined only for a specific DCI format such as 0/1A/3/3A/1C corresponding to a purpose such as a system message or power control for a UE group. DCI format with spatial multiplexing is not supported in the common search space. The downlink DCI format to be decoded in the UE-specific search space varies according to a transmission mode configured for the corresponding UE. Since the setting of the transmission mode is made through RRC signaling, the exact subframe number for whether the setting is effective for the corresponding terminal is not specified. Accordingly, the terminal can be operated so as not to lose communication by always performing decoding for DCI format 1A regardless of the transmission mode.

In the above, a method and a search space for transmitting and receiving a downlink control channel and downlink control information in conventional LTE and LTE-A have been described.

Hereinafter, a downlink control channel in the currently discussed 5G communication system will be described in more detail with reference to the drawings.

3 is a diagram illustrating an example of a basic unit of time and frequency resources constituting a downlink control channel that can be used in a 5G communication system. According to FIG. 3, the basic unit (REG) of time and frequency resources constituting the control channel consists of 1 OFDM symbol 301 on the time axis and 12 subcarriers 302 on the frequency axis, that is, 1 RB. Consists of. In configuring the basic unit of the control channel, the data channel and the control channel can be time-multiplexed within one subframe by assuming that the time axis basic unit is 1 OFDM symbol 301 . By placing the control channel ahead of the data channel, the user's processing time can be reduced, so it is easy to satisfy the delay time requirement. By setting the frequency axis basic unit of the control channel to 1 RB 302, frequency multiplexing between the control channel and the data channel can be performed more efficiently.

By concatenating REGs 303 shown in FIG. 3, control channel regions of various sizes can be set. For example, if a basic unit to which a downlink control channel is allocated in 5G is referred to as a CCE 304 , one CCE 304 may include a plurality of REGs 303 . Taking the REG 304 shown in FIG. 3 as an example, the REG 303 may be composed of 12 REs, and if 1 CCE 304 is composed of 6 REGs 303, 1 CCE 304 is It means that it can be composed of 72 REs. When the downlink control region is set, the corresponding region may be composed of a plurality of CCEs 304, and a specific downlink control channel is mapped to one or more CCEs 304 according to the aggregation level (AL) in the control region and transmitted. can be CCEs 304 in the control area are divided by numbers, and in this case, numbers may be assigned according to a logical mapping method.

The basic unit of the downlink control channel shown in FIG. 3 , that is, the REG 303 , may include both REs to which DCI is mapped and a region to which the DMRS 305 , which is a reference signal for decoding them, is mapped. The DMRS 305 may be mapped and transmitted in consideration of the number of antenna ports used to transmit a downlink control channel. 3 shows an example in which two antenna ports are used. In this case, there may be a DMRS 306 transmitted for antenna port #0 and a DMRS 307 transmitted for antenna port #1. DMRS for different antenna ports may be multiplexed in various ways. 3 shows an example in which DMRSs corresponding to different antenna ports are transmitted orthogonally in different REs. In this way, FDM may be transmitted, or CDM may be transmitted. In addition, various types of DMRS patterns may exist, which may be related to the number of antenna ports.

4 is a diagram illustrating an example of a control region (Control Resource Set, CORESET) in which a downlink control channel is transmitted in a 5G wireless communication system. In FIG. 4, two control regions (control region #1 401) within a system bandwidth 410 on the frequency axis and one slot 420 on the time axis (in the example of FIG. 4, one slot is assumed to be 7 OFDM symbols). , an example in which control area #2 (402)) is set is shown. The control regions 401 and 402 may be set to a specific subband 403 within the entire system bandwidth 410 on the frequency axis. One or a plurality of OFDM symbols may be set on the time axis, and the number of these symbols may be defined as a control region length (Control Resource Set Duration, 404). In the example of FIG. 4 , the control region #1 401 is set to a control region length of 2 symbols, and the control region #2 402 is set to a control region length of 1 symbol.

In the 5G communication system, multiple control areas may be set in one system from the point of view of the base station. Also, from the viewpoint of the terminal, a plurality of control regions may be configured for one terminal. In addition, some control regions among the control regions set in the system may be configured for the terminal. Therefore, the terminal may not know whether there is a specific control region existing in the system. To explain with a specific example, in FIG. 4 , two control areas are set in the system, a control area #1 (401) and a control area #2 (402), and a control area #1 (401) is set for the terminal #1. The terminal #2 may be configured with a control region #1 (401) and a control region #2 (402). In this case, if there is no additional indicator, the terminal #1 may not know whether the control region #2 402 exists.

The control region in the 5G wireless communication system described above may be set by the base station to the terminal through higher layer signaling (eg, system information, remote radio control (RRC) signaling). Setting the control region to the terminal means providing information such as the location of the control region, subbands, resource allocation of the control region, and the length of the control region. For example, the base station may include at least one of the following information on the control region by setting the control region in the terminal.

[Table 3]

In addition to the above configuration information, various pieces of information necessary for transmitting the downlink control channel may be configured for the terminal.

In the above, the downlink control channel in the currently discussed 5G communication system has been described.

Hereinafter, a method of reusing a control region configured to transmit a downlink control channel in a 5G communication system for data channel transmission will be described in detail.

In the 5G communication system, in order to increase resource efficiency, a function of reusing a part of the control area for data channel transmission is provided. More specifically, the base station may use time/frequency resources not actually used for DCI transmission in the control region for data channel transmission, and by transmitting an indicator indicating whether the control region is reused to the terminal, the terminal It is possible to correctly receive the data channel. Additionally, in reusing the control region for data channel transmission, if the resource region for transmitting the data channel overlaps the DCI transmission region containing the scheduling information for the data channel, the overlapping data channel is rate-matched. matching) can be transmitted. Rate matching is not allowed for other DCIs, and the control area cannot be reused for data channel transmission.

The present invention proposes a method for transmitting and receiving DCI between a base station and a terminal in an environment in which a data channel can be transmitted while reusing a control region. In the present invention, the UE may preferentially detect a DCI format related to DL assignment through blind decoding, and obtain scheduling information for a corresponding downlink data channel therefrom. In this case, the UE can determine whether the transmission of the downlink data channel has occurred when a part of the control region is reused. If the control region is reused, it is assumed that no additional DCI is transmitted in the search space existing in the corresponding region. can do. Therefore, blind decoding for other DCI formats can be performed only on the remaining search space except for the reused resource region, and from this, the number of blind decodings of the UE can be effectively reduced. The base station may perform scheduling in consideration of resource reuse for the control region when scheduling the DCI and the data channel. In this case, the base station may determine whether to use the corresponding control region for the data channel by determining to what extent the time/frequency resource to which the data channel is to be allocated overlaps with the search space of the corresponding terminal. In addition, resource allocation can be performed within the entire search space for DCIs containing scheduling information for a corresponding data channel, and resource allocation can be performed for other DCIs in a search space existing in a control region that does not overlap with the data channel. can be done

5 is a diagram illustrating an example of transmitting a downlink data channel while reusing a control region considered in a 5G communication system.

FIG. 5 shows an example in which the control region 503 (CORESET) is set in the time and frequency resources of the system bandwidth 501 on the frequency axis and one slot 502 on the time axis. In FIG. 5, the control region is allocated over 2 OFDM symbols on the time axis (that is, the control region length 510 = 2 symbols). 5 shows an example in which two different DCIs are transmitted within the control region 503 . DCI#1 504 is a DCI corresponding to downlink scheduling assignment, that is, a DCI containing scheduling information for a PDSCH 506 or 507 or 508, and DCI#2 505 is a DCI containing other information, For example, DCI corresponding to uplink scheduling grant.

In an example shown in FIG. 5 , the PDSCH may be transmitted by being mapped to a time/frequency resource 509 that is not used for DCI transmission in the control region. More specifically, the following methods may be considered.

Option 1

When a time and frequency resource for transmitting the PDSCH overlaps a region configured as a control region, and no DCI is transmitted through the overlapping resource, the resource may be reused for PDSCH transmission. For example, in the case of the PDSCH 506 in FIG. 5 , since no DCI is transmitted on the resource to which the PDSCH 506 is allocated, it may be mapped to and transmitted to an unused resource 509 in the control region. Accordingly, the PDSCH 506 may be mapped and transmitted from the first OFDM symbol at the corresponding frequency position.

Option 2

When the time and frequency resources for transmitting the PDSCH overlap a region set as the control region, and DCI containing scheduling information for the corresponding PDSCH is mapped and transmitted in all or part of the overlapping region, the PDSCH is reused in the control region. and can be transmitted. In this case, the PDSCH may be transmitted by rate matching with respect to a portion overlapping the DCI transmission resource among the resource regions in which the PDSCH is transmitted. For example, in FIG. 5, when DCI#1 504 corresponds to scheduling control information for the PDSCH 507, the PDSCH 507 is rate-matched in the resource region in which the DCI#1 504 is transmitted, and is not used otherwise. Resources in the control region that are not used may be reused for PDSCH 507 transmission. Accordingly, the PDSCH 507 may be mapped and transmitted from the first OFDM symbol at the corresponding frequency position, and rate matching may be performed in the resource region in which the DCI#1 504 is transmitted.

Since the terminal can acquire DCI#1 504 through blind decoding, and can acquire information on resources used for DCI#1 504 from this, which of the resources to which the PDSCH 507 is allocated? It is implicitly known whether the part is rate matched. Accordingly, the UE can successfully decode the PDSCH 507 .

Option 3

When the time and frequency resources for transmitting the PDSCH overlap a region set as the control region, and a DCI that does not correspond to the scheduling information for the PDSCH is mapped and transmitted in all or part of the overlapping region, the PDSCH is the resource of the control region. cannot be reused and transmitted. For example, in FIG. 5, when DCI#2 505 corresponds to control information for uplink grant, the PDSCH 508 cannot be transmitted in a region overlapping with DCI#2 505 among resources in the control region, so control It may be transmitted from the third OFDM symbol that is later in time than the region length 510 .

In the above, a method for reusing the control area for data channel transmission in the 5G communication system has been described.

The present invention proposes a method for effectively transmitting and receiving DCI between a base station and a terminal in an environment in which a data channel can be transmitted while reusing a control region.

In the present invention, when performing blind decoding on DCI, the UE may preferentially perform blind decoding on a specific DCI format and may perform reduced blind decoding on other DCI formats. That is, the UE may sequentially perform blind decoding according to the type of DCI, thereby obtaining a benefit of reducing power consumption of the UE.

In the present invention, the base station may determine whether to reuse the control region when transmitting the PDSCH of a terminal based on the degree of overlap between the search space of the corresponding terminal and the PDSCH transmission resource. This may be determined based on a specific threshold, and the threshold may be determined by the base station under determination. Accordingly, it is possible to effectively adjust a trade-off between an increase in resource efficiency due to resource reuse in the control region and a reduction in power consumption of the terminal.

In the present invention, when the base station allocates resources for DCI, a specific DCI format may be allocated to the entire search space area, and other DCI formats may be allocated to a partial search space area. Accordingly, control region resources can be more effectively reused for data channel transmission.

Hereinafter, a method and apparatus for transmitting and receiving DCI proposed by the present invention in a 5G communication system will be described through specific embodiments.

<First embodiment>

A first embodiment of the present invention relates to a method for a terminal to perform blind decoding on DCI.

6 is a view showing a first embodiment of the present invention.

6 illustrates an example in which the PDSCH 603 is transmitted while reusing resources within the control region 600 in an environment in which one control region 600 exists within the system bandwidth 608 . A search space 601 of a corresponding terminal exists in the control region 600 , and the search space 601 may be defined as a set of PDCCH candidate groups 606 . The base station may map the DCI of the terminal to a specific PDCCH candidate group 606 in the search space 601 of the terminal and transmit, and the terminal transmits its DCI to the PDCCH candidate groups 606 corresponding to the search space 601. DCI can be obtained by performing blind decoding.

6 shows an example in which two DCIs, DCI#1 (604) and DCI#2 (605) are transmitted. DCI#1 (604) may correspond to a DCI format related to downlink assignment that contains scheduling information for the PDSCH (603), and DCI#2 (605) is DCI transmitted for other purposes. Corresponds to the format (eg, uplink scheduling grant, power control, pre-emption indicator, slot format indicator, bandwidth part indicator, etc. may be considered) can do. DCI#1 604 and DCI#2 605 may be respectively mapped and transmitted to a specific PDCCH candidate group 606 in the search space 601 .

In an example shown in FIG. 6 , the PDSCH 603 can reuse resources in the control region 600 , and a partial region reused in the control region 600 is denoted by 608 . At this time, as described above, DCI#1 604 scheduling the PDSCH 603 may be transmitted to a specific PDCCH candidate group 606 existing in the reuse region 608, and DCI#1 604 may be transmitted. In a resource region to be used, the PDSCH 603 may be rate-matched and transmitted.

The UE may obtain DCI#1 (604) through blind decoding for the entire search space (601), and may obtain resource allocation information for the PDSCH (603) from DCI#1 (604). In addition, from the obtained resource allocation information for the PDSCH 603, the UE determines whether the corresponding PDSCH 603 is transmitted while reusing resources in the control region (or from which OFDM symbol the corresponding PDSCH 603 is allocated) can do. From this, the UE can recognize the reuse region 608 of the control region 600, and determines whether DCI#1 604 obtained through blind decoding is transmitted to a specific PDCCH candidate group 606 in the reuse region 608. can judge If DCI#1 604 is transmitted within the reuse region 608, the UE may assume that the received PDSCH 603 is rate-matched in the resource in which the DCI#1 604 is transmitted, and the PDSCH 603 ) can be decoded correctly. If DCI#1 604 is not transmitted in the reuse region 608, the UE may assume that no DCI is transmitted to the search space 601 existing in the reuse region 608, and accordingly, the reuse region Decoding may be performed without the assumption that a part of the PDSCH 603 transmitted to the 608 is rate-matched. That is, the UE can successfully decode the PDSCH 603 for both the case where the DCI#1 604 is transmitted within the reuse region 608 and the case where it is not.

As described above, the UE can obtain resource allocation information for the PDSCH 603 from DCI#1 604 obtained through blind decoding, and accordingly, whether resources in the control region are reused for PDSCH 603 transmission. (or from which OFDM symbol the corresponding PDSCH 603 is allocated), that is, the reuse region 608 can be recognized. Also, the UE may assume that no DCI other than the DCI for scheduling the PDSCH 603 is transmitted within the reuse region 608 . Accordingly, when the UE performs blind decoding on another DCI format from the point in time when DCI for scheduling the PDSCH 603 is obtained, the remaining search space (or , it is possible to perform blind decoding only on the partial search space (602). For example, in FIG. 6, when the UE performs blind decoding on DCI#2 605, blind decoding is performed only for the PDCCH candidate group 606 existing in the remaining search space 602 except for the search space existing in the reuse region 608. can be performed. Accordingly, it is possible to reduce the number of blind decodings for the remaining DCI formats except for DCI#1 (604).

7 is a diagram illustrating an operation of a terminal according to the first embodiment of the present invention.

In step 701, the UE may preferentially perform blind decoding on the DCI format corresponding to the downlink scheduling assignment. In this case, the terminal may perform blind decoding on the entire search space. In step 702, the UE may determine whether blind decoding is successful with respect to the DCI format corresponding to the downlink scheduling assignment.

If the terminal succeeds in blind decoding on the DCI format corresponding to the downlink scheduling assignment in step 702, the terminal may obtain scheduling information for the PDSCH from the DCI detected in step 703. The UE can know the resource allocation information of the PDSCH from the scheduling information of the PDSCH, and from this, it can know whether the resources in the control region are reused for the corresponding PDSCH transmission. In step 704, the UE receives the remaining DCI formats other than the DCI format corresponding to the downlink scheduling assignment (eg, uplink scheduling grant (Uplink Grant), power control (Power control), pre-emption indicator, slot format indicator), Blind decoding for a bandwidth part indicator (Bandwidth Part Indicator), etc. may be considered, and these are collectively referred to as “other DCI format”) may be started.

In step 705, in the process of performing blind decoding on the “other DCI formats,” the UE may determine whether a PDCCH candidate group for which blind decoding is to be performed corresponds to the previously acquired resource used for PDSCH transmission. If it is determined that the resource allocated to the PDCCH candidate group to which the corresponding blind decoding is to be performed is not used for PDSCH transmission, the UE may perform blind decoding on the corresponding PDCCH candidate group in step 706 . If it is determined that the resource allocated to the corresponding PDCCH candidate group is used for PDSCH transmission, the UE may omit blind decoding for the corresponding PDCCH candidate group in step 707 . As a result, in performing blind decoding on “other DCI formats,” the UE may perform blind decoding only on the remaining search space (or partial search space) except for the resource region used for PDSCH transmission.

The terminal may determine whether blind decoding for "other DCI formats" is successful in step 708, and if successful, the terminal may acquire the corresponding DCI in step 709, and if not successful, end the operation can do.

If the UE does not succeed in blind decoding on the DCI format corresponding to the downlink scheduling assignment in step 702, the UE performs blind decoding on “other DCI formats” except for the DCI format corresponding to the downlink scheduling assignment in step 710 can start The UE determines whether blind decoding for “other DCI formats” is successful in step 711. If the UE succeeds in blind decoding for “other DCI formats”, the UE may acquire the corresponding DCI in step 709, and if not successful, may terminate the operation.

<Second embodiment>

A second embodiment of the present invention relates to a method for scheduling a PDSCH in a base station.

8 is a diagram illustrating a second embodiment of the present invention.

8 shows an example in which the control region 800 of one terminal is set within the system bandwidth 810, and in this case, the control region length 811 is set to two OFDM symbols. In the control region 800 , the entire search space 801 including a set of PDCCH candidate groups 802 of the corresponding UE may exist. When the base station allocates the PDSCH resource to the corresponding terminal, the resource in the control region 800 can be reused and allocated, and at this time, whether the resource is reused (ie, from which OFDM symbol the PDSCH is allocated on the time axis) may be determined in consideration of the search space 801 of the corresponding terminal.

More specifically, a frequency-axis resource to which a PDSCH of one terminal is to be allocated may overlap with a frequency-axis resource set as a control region. In this case, in determining the time axis resource allocation of the PDSCH, it may be considered whether to reuse the resources in the corresponding control region. If it is determined that resources in the control region may be reused, the PDSCH may be mapped starting from a symbol (eg, the first symbol) including the control region. Conversely, when it is determined that resources in the control region are not to be reused, the PDSCH may be mapped starting from a symbol that does not include the control region (the third symbol in the example of FIG. 8 ).

At this time, the base station determines whether or not the PDSCH reuses resources in the control region, based on the search space of the corresponding terminal and “Overlapping Ratio” when the PDSCH is mapped by reusing resources in the control region. can do. For example, if it is assumed that the PDSCH reuses the transmission resources in the control region, the PDSCH transmission resources and the transmission resources allocated to some PDCCH candidates in the search space in the control region may overlap as a specific resource of the control region is reused. In this case, the ratio of the PDCCH candidates overlapped with the PDSCH transmission resource among the PDCCH candidates in the entire search space may be defined as an “overlapping ratio”, and this overlapping ratio may be expressed, for example, as in Equation 1 below.

[Equation 1]

Overlapping Ratio = (the number of PDCCH candidates overlapped with the PDSCH transmission resource) / (the total number of PDCCH candidates)

Similarly, the overlap ratio described above may be interpreted as a non-overlapping ratio, and the non-overlapping ratio may be expressed as, for example, “1-overlapping ratio”. The base station may determine whether the overlapping ratio (or non-overlapping ratio) defined above is greater than or less than the threshold based on a specific threshold. If the overlap ratio is greater than a specific threshold (or if the non-overlapping ratio is less than a specific threshold), when the PDSCH is transmitted by reusing resources in the control region, it means that the number of PDCCH candidates for transmitting control information is excessively reduced. can do. Accordingly, the base station may determine that the control region resource will not be reused for the corresponding PDSCH, and may determine the time axis resource allocation of the PDSCH accordingly. Conversely, if the overlap ratio is smaller than a specific threshold (or if the non-overlapping ratio is greater than a specific threshold), it means that there are enough PDCCH candidates to transmit control information even if the PDSCH is transmitted by reusing resources in the control region. can do. Accordingly, the base station may determine to reuse the control region resources for the corresponding PDSCH, and thus may determine the time axis resource allocation of the corresponding PDSCH. That is, the base station may determine the number of the OFDM symbol in which the PDSCH resource allocation starts.

A specific example will be described with reference to the drawings shown in FIG. 8 . In the example of FIG. 8 , the entire search space 801 includes a total of 10 PDCCH candidate groups 802 . Also, let us assume that the threshold ( η ) to be compared with the overlap ratio is 45%. This threshold may be a value predetermined by the terminal and/or the base station, and may be shared in advance between the terminal and the base station through a physical layer signal or a higher layer signal.

For example, the base station may first determine the frequency axis resource of the PDSCH#1 804 of a certain terminal, and may determine whether to reuse the resource in the control region 800 of the corresponding terminal. In the example of FIG. 8 , when the PDSCH#1 804 reuses resources in the control region 800 , that is, when time-axis resource allocation is made from the first OFDM symbol, the PDSCH#1 804 is the entire search space 801 . ) may overlap with a total of 5 PDCCH candidate groups among the 10 PDCCH candidate groups 802 within. Accordingly, the overlap ratio may be calculated as 50%. Since the threshold value determined by the base station is 45% and the overlap ratio is greater than the predetermined threshold value, the base station may determine not to reuse the resources in the control region 800 for PDSCH#1 804. This is because, when the PDSCH#1 804 is transmitted by reusing resources in the control region 800, scheduling diversity for other DCI formats may not be sufficiently secured. Accordingly, the time axis resource allocation of the PDSCH#1 804 may be determined as the third OFDM symbol, which is a symbol that does not include the control region 804 .

As another example, the base station may first determine the frequency axis resource of the PDSCH#2 805 of a terminal, and may determine whether to reuse the resource in the control region 800 of the corresponding terminal. In the example of FIG. 8, when PDSCH#2 804 reuses resources in the control region 800, that is, when time-axis resource allocation is made from the first OFDM symbol, 10 PDCCH candidate groups in the entire search space 801 ( 802) may overlap with a total of four PDCCH candidates. Accordingly, the overlap ratio may be calculated as 40%. Since the threshold value determined by the base station is 45% and the overlap ratio is smaller than the predetermined threshold value, the base station may determine to reuse the resources in the control region 800 for PDSCH#2 (805). This is because it was determined that scheduling diversity for other DCI formats can be sufficiently secured even when the PDSCH#2 805 is transmitted by reusing the resources in the control region 800 . Accordingly, the time axis resource allocation of the PDSCH#2 (805) may be determined as the first OFDM symbol, which is a symbol including the control region (804). 8 shows a result of resource allocation of PDSCH#2 (805) by the base station reusing (806) some of the control region (804).

9 is a diagram illustrating an operation of a base station according to a second embodiment of the present invention.

The base station may determine the frequency axis resource allocation for the PDSCH of a certain terminal in step 901. In step 902, the base station may first determine whether the frequency axis resource to which the PDSCH is to be allocated overlaps with the control region defined for the corresponding terminal.

If there is no control region configured in the frequency axis resource to which the PDSCH is to be allocated, the base station may determine the time axis resource allocation of the corresponding PDSCH in step 906 .

If there is a control region configured in the frequency axis resource to which the PDSCH is to be allocated, the base station may determine whether to reuse the resources in the control region for the corresponding PDSCH transmission in step 903 . According to the second embodiment of the present invention, it may be determined based on the overlap ratio of the PDSCH to be transmitted and the search space, and conversely, it may be determined based on the non-overlapping ratio. If the overlap ratio defined above is greater than the predetermined specific threshold (η ), the base station may determine not to reuse the resources in the control region for the corresponding PDSCH transmission in step 904, and accordingly, in step 906, the time of the corresponding PDSCH Axis resource allocation can be determined. That is, in determining the time axis resource allocation for the PDSCH, it is possible to map from symbols not including the control region. Conversely, if the overlap ratio is smaller than a predetermined specific threshold η , the base station may determine to reuse the resources in the control region for the corresponding PDSCH transmission in step 905, and accordingly determine the time axis resource allocation of the corresponding PDSCH in step 906 can That is, in determining the time axis resource allocation for the PDSCH, it is possible to map from the symbol (eg, the first symbol) including the control region.

In the second embodiment of the present invention, the base station can adjust the frequency of reusing the control region for PDSCH transmission by adjusting the threshold defined above.

For example, the larger the threshold value is set, the greater the control area reuse rate may be. That is, the base station can reuse the resources in the control region with a higher probability for PDSCH transmission as the threshold is set larger. Accordingly, it is advantageous to increase the utilization efficiency of the entire resource by more actively reusing the unused control region for the PDSCH. This may be advantageous when a relatively small number of terminals exist in a corresponding system or when the number of DCIs to be transmitted by the base station is small in a low traffic environment.

For example, as the threshold value is set smaller, the control area reuse rate may decrease. That is, the base station can reuse the resources in the control region with a lower probability for PDSCH transmission as the threshold is set smaller. Accordingly, by passively reusing an unused control region for the PDSCH, it is possible to relatively increase the amount of resources available for DCI transmission in the control region. Accordingly, scheduling diversity for DCI transmission in the control region may be increased. This may be advantageous when a relatively large number of terminals exist in a corresponding system or when there are many DCIs that the base station needs to transmit in a high traffic environment.

When the second embodiment of the present invention is used in combination with the first embodiment of the present invention, the number of blind decodings of the terminal may be adjusted according to a threshold value defined by the base station.

For example, as the threshold value increases, the control region reuse rate may increase, which means that resources in the control region are more actively reused for PDSCH transmission. This means that the number of PDCCH candidates in the search space available for allocating “other DCI formats” excluding the DCI format corresponding to DL allocation is reduced. Therefore, as the threshold value increases when the base station performs <the second embodiment>, the number of PDCCH candidates to be monitored for “other DCI formats” when the terminal performs the <first embodiment> decreases. Accordingly, the number of times of blind decoding for “other DCI formats” of the terminal may be reduced, thereby reducing the burden of blind decoding on the terminal. This may lead to a reduction in power consumption of the terminal.

Conversely, as the threshold value decreases, the control region reuse rate may decrease, which means that resources in the control region are more passively reused for PDSCH transmission. This means that the number of PDCCH candidates in the search space available for allocating “other DCI formats” excluding DCI formats corresponding to DL allocation increases. Accordingly, as the base station decreases the threshold in performing <Second Embodiment>, the number of PDCCH candidates to be monitored for “other DCI formats” in the UE performing <First Embodiment> increases. Accordingly, although the number of blind decodings for “other DCI formats” of the UE may increase, the number of PDCCH candidates to which “other DCI formats” can be allocated from the base station increases, thereby increasing scheduling diversity.

<Third embodiment>

A third embodiment of the present invention relates to a method for scheduling DCI in a base station.

10 is a diagram illustrating a third embodiment of the present invention.

10 shows an example in which the PDSCH 1003 is transmitted while reusing resources in the control region 1000 according to the second embodiment in an environment in which one control region 1000 exists within the system bandwidth 1008. have. A search space 1001 of a corresponding terminal exists in the control region 1000 , and the search space 1001 may be defined as a set of PDCCH candidate groups 1006 .

In FIG. 10, an example in which two DCIs, that is, DCI#1 (1004) and DCI#2 (1005) are transmitted is shown. DCI#1 (1004) may correspond to a DCI format related to downlink assignment that contains scheduling information for the PDSCH (1003), and DCI#2 (1005) is DCI transmitted for other purposes. Format (for example, at least one of uplink scheduling grant (Uplink Grant), power control (Power control), pre-emption indicator, slot format indicator (Slot Format Indicator), bandwidth part indicator (Bandwidth Part Indicator) may correspond) may correspond to DCI#1 (1004) and DCI#2 (1005) may be mapped to a specific PDCCH candidate group 1006 in the search space 1001 and transmitted.

In the third embodiment of the present invention, in a method for a base station to map a DCI to a specific PDCCH candidate group and transmit it, resource allocation for transmitting a DCI may be differently determined according to a DCI format. More specifically, for the DCI format corresponding to the DL scheduling assignment, the base station maps the DCI to a specific PDCCH candidate group in the entire search space (that is, a candidate group selected from among the PDCCH candidate groups in the search space reused for PDSCH transmission) and transmits it. And for “other DCI formats,” the DCI is mapped to a specific PDCCH candidate group in the remaining search space that is not reused for PDSCH transmission (that is, a candidate group selected from among PDCCH candidates other than the search space reused for PDSCH transmission). It can be transmitted. . For example, in FIG. 10 , the base station may map DCI#1 1004 corresponding to the DL scheduling assignment to one PDCCH candidate group 1006 of the entire search space 1001 and transmit it. In FIG. 10, the base station is one of the partial search spaces 1002 that are not used for PDSCH transmission, that is, do not overlap with PDSCH transmission resources, with respect to DCI#2 1005 corresponding to “other DCI formats” rather than DL scheduling assignment. It can be transmitted by mapping to the PDCCH candidate group 1006 of .

11 is a diagram illustrating an operation of a base station according to a third embodiment of the present invention.

The base station may determine the format of DCI to be scheduled in step 1101. If the DCI format to be scheduled corresponds to the DL scheduling assignment related DCI format, the base station maps the DCI to a resource corresponding to a specific PDCCH candidate group in the resource region in which the PDSCH related to the DCI format is transmitted in the entire search space in step 1102 can be transmitted. If the DCI format to be scheduled corresponds to “other DCI formats” that are not related to DL scheduling assignment, the base station converts the DCI to the partial search space existing in the control region not used for PDSCH transmission within the entire search space in step 1103. It can be transmitted by mapping to a specific PDCCH candidate group in the

In order to carry out the above embodiments of the present invention, a transmitter, a receiver, and a controller of the terminal and the base station are shown in FIGS. 12 and 13, respectively. The structures of the base station and the terminal for performing the DCI transmission method, the PDSCH scheduling method, and the blind decoding method in the 5G communication system corresponding to the above embodiments are shown. It should work according to the example.

12 is a block diagram illustrating an internal structure of a terminal according to an embodiment of the present invention. As shown in FIG. 12 , the terminal of the present invention may include a terminal processing unit 1201 , a receiving unit 1202 , and a transmitting unit 1203 .

The terminal processing unit 1201 may control a series of processes in which the terminal may operate according to the above-described embodiment of the present invention. For example, a blind decoding operation for a downlink control channel according to an embodiment of the present invention may be differently controlled. In the embodiment of the present invention, the terminal receiving unit 1202 and the terminal collectively refer to the transmitting unit 1203 as a transceiver. The transceiver may transmit/receive a signal to/from the base station. The signal may include control information and data. To this end, the transceiver may include an RF transmitter for up-converting and amplifying a frequency of a transmitted signal, and an RF receiver for low-noise amplifying and down-converting a received signal. In addition, the transceiver may receive a signal through a wireless channel, output it to the terminal processing unit 1201 , and transmit a signal output from the terminal processing unit 1201 through a wireless channel.

13 is a block diagram illustrating an internal structure of a base station according to an embodiment of the present invention. As shown in FIG. 13 , the base station of the present invention may include a base station processing unit 1301 , a receiving unit 1302 , and a transmitting unit 1303 .

The base station processing unit 1301 may control a series of processes so that the base station can operate according to the above-described embodiment of the present invention. For example, control may be performed differently according to a PDSCH scheduling method, a DCI transmission method, etc. according to an embodiment of the present invention. In addition, it can be controlled to transmit various additional indicators and setting information as needed. The base station receiving unit 1302 and the base station transmitting unit 1303 may be collectively referred to as a transceiver in the embodiment of the present invention. The transceiver may transmit/receive a signal to/from the terminal. The signal may include control information and data. To this end, the transceiver may include an RF transmitter for up-converting and amplifying a frequency of a transmitted signal, and an RF receiver for low-noise amplifying and down-converting a received signal. In addition, the transceiver may receive a signal through a wireless channel and output it to the base station processing unit 1301 , and transmit the signal output from the base station processing unit 1301 through the wireless channel.

On the other hand, the embodiments of the present invention disclosed in the present specification and drawings are merely presented as specific examples to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention. That is, it will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications can be implemented based on the technical idea of the present invention. In addition, each of the above embodiments may be operated in combination with each other as needed.

Claims (20)

A method performed by a terminal of a wireless communication system, comprising:
detecting first downlink control information (DCI) for scheduling downlink data in a search space of the terminal;
determining whether the downlink data scheduled by the first DCI is mapped to a resource of a control region used for transmission of control information;
when the downlink data is mapped to the resource of the control region, detecting a second DCI in a portion of the search space except for the resource to which the downlink data is mapped; and
and detecting the second DCI in the entire search space of the terminal when the downlink data is not mapped to the resource of the control region. According to claim 1,
When the downlink data is mapped to the resource of the control region and the first DCI is detected in the resource, the terminal rate-matches the resource to which the first DCI is mapped in the control region. Decoding the downlink data assuming that According to claim 1,
The determining may further include determining based on a start Orthogonal Frequency Division Multiplexing (OFDM) symbol to which the downlink data is mapped. According to claim 1,
The second DCI includes information on at least one of an uplink scheduling grant, power control, a pre-emption indicator, a slot format indicator, and a bandwidth partial indicator. In the terminal of a wireless communication system,
a transceiver configured to transmit or receive a signal; and
comprising a control unit;
The control unit is:
Detects first downlink control information (DCI) for scheduling downlink data in the search space of the terminal,
determining whether the downlink data scheduled by the first DCI is mapped to a resource of a control region used for transmission of control information;
If the downlink data is mapped to the resource of the control region, detecting a second DCI in a part of the search space except for the resource to which the downlink data is mapped,
If the downlink data is not mapped to the resource of the control region, the terminal is configured to detect the second DCI in the entire search space of the terminal. 6. The method of claim 5,
When the downlink data is mapped to the resource of the control region and the first DCI is detected in the resource, the terminal rate-matches the resource to which the first DCI is mapped in the control region. It is assumed that the decoding of the downlink data, the terminal. 6. The method of claim 5,
The control unit, based on a start OFDM (Orthogonal Frequency Division Multiplexing) symbol to which the downlink data is mapped, determines whether the downlink data is mapped to the resource of the control region, the terminal. 6. The method of claim 5,
The second DCI includes information on at least one of an uplink scheduling grant, power control, pre-emption indicator, slot format indicator, and bandwidth partial indicator, the terminal. A method performed by a base station of a wireless communication system, comprising:
determining that the first resource region mapped to downlink data to be transmitted to the terminal overlaps the second resource region used for transmission of control information;
determining whether to transmit the downlink data by mapping the downlink data on the second resource region based on the overlapping ratio of the first resource region and the second resource region;
transmitting, to the terminal, the downlink data in the entire first resource region when the overlapping ratio is less than a threshold value; and
If the overlapping ratio is equal to or greater than the threshold, transmitting the downlink data to the terminal in a portion except for the second resource region in the first resource region,
The overlapping ratio is a ratio between the number of physical downlink control channel (PDCCH) candidates in the second resource region and the number of PDCCH candidates in the overlapping region between the first resource region and the second resource region. 10. The method of claim 9,
The method is
if the overlapping ratio is less than the threshold, mapping the downlink data to a first orthogonal frequency division multiplexing (OFDM) symbol and successive OFDM symbols; and
If the overlapping ratio is equal to or greater than the threshold value, the method further comprising the step of mapping the downlink data to OFDM symbols outside the second resource region. 10. The method of claim 9,
The method is
mapping first Downlink Control Information (DCI) related to the downlink data into a resource region mapped to the downlink data; and
The method further comprising the step of mapping a second DCI not related to the downlink data to a portion remaining except for a portion overlapping the first resource region in the second resource region. In a base station of a wireless communication system,
a transceiver configured to transmit or receive a signal; and
comprising a control unit;
The control unit is:
It is determined that a first resource region mapped to downlink data to be transmitted to the terminal overlaps a second resource region used for transmission of control information,
determining whether to transmit the downlink data by mapping the downlink data on the second resource region based on the overlapping ratio of the first resource region and the second resource region;
If the overlapping ratio is less than the threshold, transmitting the downlink data in the entire first resource region to the terminal,
If the overlapping ratio is equal to or greater than the threshold value, it is configured to transmit the downlink data to the terminal in a portion except for the second resource region in the first resource region,
The overlapping ratio is a ratio between the number of physical downlink control channel (PDCCH) candidates in the second resource region and the number of PDCCH candidates in the overlapping region between the first resource region and the second resource region. 13. The method of claim 12,
The control unit is
If the overlap ratio is less than the threshold, the downlink data is mapped to a first OFDM symbol and successive OFDM symbols,
If the overlapping ratio is equal to or greater than the threshold, the base station is configured to map the downlink data to OFDM symbols outside the second resource region. 13. The method of claim 12,
The control unit is
mapping first Downlink Control Information (DCI) related to the downlink data in a resource region mapped to the downlink data;
A base station that maps a second DCI not related to the downlink data to a portion remaining except for a portion overlapping the first resource region in the second resource region. delete delete delete delete delete delete

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